1. Field of The Invention
The present invention relates to a magnetic disk storage, which is employed as a storage device for use in a computer system etc., and to a method for accessing a track in a magnetic disk storage.
2. Description of The Related Art
Generally, in a hard disk (or rigid disk) which is usually employed as a storage device for use in a computer system etc., the positioning of a magnetic head is controlled such that the magnetic head (hereunder sometimes referred to as the data head) can have access to a desired track. Various techniques have been developed to realize rapid and accurate access of a magnetic head to a desired position in a track of a hard disk. Of such techniques, the following three practical ones are utilized for accessing a track of a hard disk.
A first one is a dedicated-servo technique which uses a surface of a disk (hereunder sometimes referred to as a servo disk surface) as dedicated to the storing of a servo signal and controls the accessing of the data head to a track and the centering of the data head on the track in accordance with an output signal read from the servo disk surface.
Further, a second one is an embedded servo technique which writes a servo signal representing track position information to a sector of each track and controls the accessing of the data head to a track and the centering of the data head on the track in accordance with a head output signal read from the sector.
Additionally, a third one is a combination of the first and second techniques.
In magnetic disk storages implementing the foregoing conventional techniques, the realization of quicker access of a data head to a corresponding disk (hereunder sometimes referred to as quick track access), provision of larger storage capacity by decreasing a track pitch and provision of high-speed data transfer, etc. are always required.
However, when attempting to achieve the quick track access, an error due to miscount may be generated in the detection of the position of the data head. Further, when attempting to effect the centering of the data head on the track (hereunder sometimes referred to simply as the track centering processing) with high precision, it is necessary to increase the area of a storage region to be used for storing the servo signal and thus to decrease the area of a storage region to be used for recording a data signal. Furthermore, when attempting to achieve the high-speed data transfer by effecting read/write operations by using the data heads in parallel with each other, a data writing signal, which is to be applied to a data head, may be applied to a servo head dedicated to a read operation, resulting in degradation of the signal-to-noise ratio (S/N) of the servo signal. The present invention is provided to eliminate these drawbacks of the prior art.
It is accordingly an object of the present invention to provide a magnetic disk storage which can realize the quick access of the data head to a track, the increase in the storage capacity and the high-speed data transfer by using two or more data heads in parallel with each other and a method for accessing a track of such a magnetic disk storage.